The present invention relates to a radio communication method and a radio communication unit suitably applied to a mobile phone unit, particularly to the art in which a function of making communication for a non-contact IC card is incorporated into the unit.
It has been heretofore practiced to utilize the non-contact IC card for making various data communication in a short distance. For example, the non-contact IC card is used for a railroad ticket and the like. Specifically, a reader/writer of the non-contact IC card is installed at a wicket; the non-contact IC card is brought close to the reader/writer when passing the wicket; and data stored in the non-contact IC card is read to perform authentication processing and the like.
There are two types of non-contact IC card: a type with a built-in battery and another type without a built-in battery; however, in view of easiness to handle, an operational life and so on, recently the type without a built-in battery has widely been used. In the case where the non-contact IC card without a battery is used, an electric power wave is supplied from the reader/writer side; an antenna on the side of IC card receives the electric power wave to store power in a capacitor in the IC card; and the stored power is utilized for driving the IC card. Thus, the IC card must be brought very close to the reader/writer.
In addition to the above-described railroad ticket, the non-contact IC card is now being applied to an electronic money card, a personal identification card such as an employee identification card and the like. In NIKKEI ELECTRONICS, No. 798, pages 55 to 60 (published by Nikkei Business Publications Inc. on Jun. 18, 2001), there is a description about this non-contact IC card. Note that although the non-contact IC card need not necessarily take a card shape, in this specification a non-contact structure for making a short-distance communication of this kind will be referred to as the non-contact IC card or IC card.
Hereupon, if the non-contact IC card is integrated with portable electronic equipment carried by the user or if the IC card can be installed in the portable electronic equipment, then it will be unnecessary to carry the relevant electronic equipment separately from the IC card and it is convenient for the user. A mobile phone unit is one of the portable electronic equipment on which such integration is assumed.
However, since the mobile phone unit is equipment that transmits and receives an electric wave, when it is assumed that the mobile phone unit is integrated with the non-contact IC card, a radio signal exchanged between the IC card and reader/writer will very likely make an undesirable effect on a signal used in radio telephone communication between the mobile phone unit and a base station or the like.
Conventionally, a frequency bandwidth of the radio signal used in the mobile phone system (from several hundred MHz to several GHz, for example) is different from a frequency bandwidth of the radio signal exchanged between the non-contact IC card and reader/writer (several tens of MHz, for example). However, harmonics of the radio signal transmitted between the non-contact IC card and reader/writer will most likely be a jamming wave against the radio signal used in the mobile phone system.
Therefore, when a function of IC card for non-contact communication of this kind is incorporated in the mobile phone unit, such measures as: adding an anti-interference exclusive circuit to the unit in accordance with a radio communication frequency and a controller-operating clock frequency as the IC card as well as a radio communication frequency and a controller-operating clock frequency as the mobile phone; shielding inside the equipment a circuit portion functioning as the mobile phone unit and a circuit portion functioning as the non-contact IC card from being interfered with each other; and the like are required, which poses a problem to make the structure of equipment complicated.
The present invention has been made in view of the above problems and aims to prevent without difficulty the mutual interference when the non-contact IC card function is incorporated into the mobile phone unit.